Info

larger numbers of processors (> 64) can be explained by load imbalances and the time required to synchronize processors at the required frame rate. The efficiencies would be higher for a larger image.

Table 2 shows the improvements that were obtained through the data bricking and spatial hierarchy optimizations.

5 Example Applications

In this last section, we give examples of the NOISE, view-dependent, and real-time ray tracing algorithms given in the three previous sections. The examples we chose are from large medical imaging data sets, as well as from a large-scale geoscience imaging data set. Further examples of each of the algorithms along with detailed performance analyses can be found in our recent papers on isosurface extraction [16,25,29,35,36]. Figure 15 shows NOISE examples; Fig. 16 shows view-dependent examples, and Figs. 17 and 18 show examples of real-time ray tracing.

TABLE 2 Times in seconds for optimizations for ray tracing the visible humana

View

"A 512 x 512 image was generated on 16 processors using a single view of an isosurface.

FIGURE 15 Mantle convection modeling that was done on a Cray T3D at the Advanced Computing Laboratory at Los Alamos National Laboratory using more than 20 million elements. The left image shows a single, hot, isosurface, while the second adds a cold (blue) transparent isosurface. The third image shows a slice through the mantle with a single isosurface. See also Plate 133.

FIGURE 15 Mantle convection modeling that was done on a Cray T3D at the Advanced Computing Laboratory at Los Alamos National Laboratory using more than 20 million elements. The left image shows a single, hot, isosurface, while the second adds a cold (blue) transparent isosurface. The third image shows a slice through the mantle with a single isosurface. See also Plate 133.

Initial Bricking Hierarchy + bricking

FIGURE 16 Full vs view-dependent isosurface extraction. The isosurfaces were computed based on a user point of view that was above and behind the skull. These images illustrate the large portions of the isosurface that the view-dependent algorithm was able to avoid. See also Plate 134.

FIGURE 17 Ray tracings of the bone and skin isosurfaces of the visible woman. See also Plate 135.

FIGURE 18 A ray tracing with and

without shadows. See also Plate 136.

Acknowledgments

This work was supported in part by awards from the Department of Energy and the National Science Foundation. The authors thank Peter Shirley, Chuck Hansen, Han-Wei Shen, and Peter-Pike Sloan for their significant contributors to the research presented in this chapter. The Visible Woman data set was obtained from the Visible Human Project of the National Library of Medicine.